Fence Post Depth Calculator
Calculate ideal post burial depth and total post length from fence height and depth ratio.
What Is a Fence Post Depth Calculator?
A fence post depth calculator finds how deep to bury fence posts and what total post length to buy. Enter above-ground fence height and a burial ratio to get hole depth and lumber length.
Post Depth Formulas
$$ \text{Post depth} = \text{Fence height} \times \text{Ratio} $$
$$ \text{Post length} = \text{Fence height} \times (1 + \text{Ratio}) $$
The minimum standard ratio is 1/3 (0.33), meaning one-third of total post length sits underground. For concrete volume, see the Fence Calculator. For total project cost, try the Fence Cost Calculator.
Frequently Asked Questions
How deep should a 6-foot fence post be buried?
At the 1/3 ratio, bury about 1.98 feet (roughly 24 inches). Total post length should be about 7.98 feet. Buy 8-foot posts or longer.
What is the minimum post burial depth?
At least one-third of the total post length should be underground. For a 6-foot above-ground fence, that means roughly 2 feet of burial depth.
Should I use 1/3 or 2/5 burial ratio?
Use 1/3 for normal soil and moderate wind. Use 2/5 (0.40) or 1/2 (0.50) in sandy soil, high wind, or heavy solid fencing that catches more wind load.
How much concrete does a 4x4 post need?
For a 6-foot fence with a 10-inch diameter hole about 2 feet deep, plan on roughly 0.5 to 1 cubic foot of concrete per post, or 2 to 4 bags of 50-lb premix.
Why buy posts longer than calculated?
Extra length covers uneven ground, trimming, and setting errors. Add a few inches beyond the calculated total post length when purchasing.
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